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Revision 612 - (show annotations) (download)
Sat Jul 2 15:20:59 2011 UTC (2 years, 9 months ago) by ph10
File size: 33538 byte(s)
Fix two study bugs concerned with minimum subject lengths; add features to 
pcretest so that all tests can be run with or without study; adjust tests so 
that this happens.

1 .TH PCRETEST 1
2 .SH NAME
3 pcretest - a program for testing Perl-compatible regular expressions.
4 .SH SYNOPSIS
5 .rs
6 .sp
7 .B pcretest "[options] [input file [output file]]"
8 .sp
9 \fBpcretest\fP was written as a test program for the PCRE regular expression
10 library itself, but it can also be used for experimenting with regular
11 expressions. This document describes the features of the test program; for
12 details of the regular expressions themselves, see the
13 .\" HREF
14 \fBpcrepattern\fP
15 .\"
16 documentation. For details of the PCRE library function calls and their
17 options, see the
18 .\" HREF
19 \fBpcreapi\fP
20 .\"
21 documentation. The input for \fBpcretest\fP is a sequence of regular expression
22 patterns and strings to be matched, as described below. The output shows the
23 result of each match. Options on the command line and the patterns control PCRE
24 options and exactly what is output.
25 .
26 .
27 .SH COMMAND LINE OPTIONS
28 .rs
29 .TP 10
30 \fB-b\fP
31 Behave as if each pattern has the \fB/B\fP (show byte code) modifier; the
32 internal form is output after compilation.
33 .TP 10
34 \fB-C\fP
35 Output the version number of the PCRE library, and all available information
36 about the optional features that are included, and then exit.
37 .TP 10
38 \fB-d\fP
39 Behave as if each pattern has the \fB/D\fP (debug) modifier; the internal
40 form and information about the compiled pattern is output after compilation;
41 \fB-d\fP is equivalent to \fB-b -i\fP.
42 .TP 10
43 \fB-dfa\fP
44 Behave as if each data line contains the \eD escape sequence; this causes the
45 alternative matching function, \fBpcre_dfa_exec()\fP, to be used instead of the
46 standard \fBpcre_exec()\fP function (more detail is given below).
47 .TP 10
48 \fB-help\fP
49 Output a brief summary these options and then exit.
50 .TP 10
51 \fB-i\fP
52 Behave as if each pattern has the \fB/I\fP modifier; information about the
53 compiled pattern is given after compilation.
54 .TP 10
55 \fB-M\fP
56 Behave as if each data line contains the \eM escape sequence; this causes
57 PCRE to discover the minimum MATCH_LIMIT and MATCH_LIMIT_RECURSION settings by
58 calling \fBpcre_exec()\fP repeatedly with different limits.
59 .TP 10
60 \fB-m\fP
61 Output the size of each compiled pattern after it has been compiled. This is
62 equivalent to adding \fB/M\fP to each regular expression.
63 .TP 10
64 \fB-o\fP \fIosize\fP
65 Set the number of elements in the output vector that is used when calling
66 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP to be \fIosize\fP. The default value
67 is 45, which is enough for 14 capturing subexpressions for \fBpcre_exec()\fP or
68 22 different matches for \fBpcre_dfa_exec()\fP. The vector size can be
69 changed for individual matching calls by including \eO in the data line (see
70 below).
71 .TP 10
72 \fB-p\fP
73 Behave as if each pattern has the \fB/P\fP modifier; the POSIX wrapper API is
74 used to call PCRE. None of the other options has any effect when \fB-p\fP is
75 set.
76 .TP 10
77 \fB-q\fP
78 Do not output the version number of \fBpcretest\fP at the start of execution.
79 .TP 10
80 \fB-S\fP \fIsize\fP
81 On Unix-like systems, set the size of the run-time stack to \fIsize\fP
82 megabytes.
83 .TP 10
84 \fB-s\fP
85 Behave as if each pattern has the \fB/S\fP modifier; in other words, force each
86 pattern to be studied. If the \fB/I\fP or \fB/D\fP option is present on a
87 pattern (requesting output about the compiled pattern), information about the
88 result of studying is not included when studying is caused only by \fB-s\fP and
89 neither \fB-i\fP nor \fB-d\fP is present on the command line. This behaviour
90 means that the output from tests that are run with and without \fB-s\fP should
91 be identical, except when options that output information about the actual
92 running of a match are set. The \fB-M\fP, \fB-t\fP, and \fB-tm\fP options,
93 which give information about resources used, are likely to produce different
94 output with and without \fB-s\fP. Output may also differ if the \fB/C\fP option
95 is present on an individual pattern. This uses callouts to trace the the
96 matching process, and this may be different between studied and non-studied
97 patterns. If the pattern contains (*MARK) items there may also be differences,
98 for the same reason. The \fB-s\fP command line option can be overridden for
99 specific patterns that should never be studied (see the /S option below).
100 .TP 10
101 \fB-t\fP
102 Run each compile, study, and match many times with a timer, and output
103 resulting time per compile or match (in milliseconds). Do not set \fB-m\fP with
104 \fB-t\fP, because you will then get the size output a zillion times, and the
105 timing will be distorted. You can control the number of iterations that are
106 used for timing by following \fB-t\fP with a number (as a separate item on the
107 command line). For example, "-t 1000" would iterate 1000 times. The default is
108 to iterate 500000 times.
109 .TP 10
110 \fB-tm\fP
111 This is like \fB-t\fP except that it times only the matching phase, not the
112 compile or study phases.
113 .
114 .
115 .SH DESCRIPTION
116 .rs
117 .sp
118 If \fBpcretest\fP is given two filename arguments, it reads from the first and
119 writes to the second. If it is given only one filename argument, it reads from
120 that file and writes to stdout. Otherwise, it reads from stdin and writes to
121 stdout, and prompts for each line of input, using "re>" to prompt for regular
122 expressions, and "data>" to prompt for data lines.
123 .P
124 When \fBpcretest\fP is built, a configuration option can specify that it should
125 be linked with the \fBlibreadline\fP library. When this is done, if the input
126 is from a terminal, it is read using the \fBreadline()\fP function. This
127 provides line-editing and history facilities. The output from the \fB-help\fP
128 option states whether or not \fBreadline()\fP will be used.
129 .P
130 The program handles any number of sets of input on a single input file. Each
131 set starts with a regular expression, and continues with any number of data
132 lines to be matched against the pattern.
133 .P
134 Each data line is matched separately and independently. If you want to do
135 multi-line matches, you have to use the \en escape sequence (or \er or \er\en,
136 etc., depending on the newline setting) in a single line of input to encode the
137 newline sequences. There is no limit on the length of data lines; the input
138 buffer is automatically extended if it is too small.
139 .P
140 An empty line signals the end of the data lines, at which point a new regular
141 expression is read. The regular expressions are given enclosed in any
142 non-alphanumeric delimiters other than backslash, for example:
143 .sp
144 /(a|bc)x+yz/
145 .sp
146 White space before the initial delimiter is ignored. A regular expression may
147 be continued over several input lines, in which case the newline characters are
148 included within it. It is possible to include the delimiter within the pattern
149 by escaping it, for example
150 .sp
151 /abc\e/def/
152 .sp
153 If you do so, the escape and the delimiter form part of the pattern, but since
154 delimiters are always non-alphanumeric, this does not affect its interpretation.
155 If the terminating delimiter is immediately followed by a backslash, for
156 example,
157 .sp
158 /abc/\e
159 .sp
160 then a backslash is added to the end of the pattern. This is done to provide a
161 way of testing the error condition that arises if a pattern finishes with a
162 backslash, because
163 .sp
164 /abc\e/
165 .sp
166 is interpreted as the first line of a pattern that starts with "abc/", causing
167 pcretest to read the next line as a continuation of the regular expression.
168 .
169 .
170 .SH "PATTERN MODIFIERS"
171 .rs
172 .sp
173 A pattern may be followed by any number of modifiers, which are mostly single
174 characters. Following Perl usage, these are referred to below as, for example,
175 "the \fB/i\fP modifier", even though the delimiter of the pattern need not
176 always be a slash, and no slash is used when writing modifiers. White space may
177 appear between the final pattern delimiter and the first modifier, and between
178 the modifiers themselves.
179 .P
180 The \fB/i\fP, \fB/m\fP, \fB/s\fP, and \fB/x\fP modifiers set the PCRE_CASELESS,
181 PCRE_MULTILINE, PCRE_DOTALL, or PCRE_EXTENDED options, respectively, when
182 \fBpcre_compile()\fP is called. These four modifier letters have the same
183 effect as they do in Perl. For example:
184 .sp
185 /caseless/i
186 .sp
187 The following table shows additional modifiers for setting PCRE compile-time
188 options that do not correspond to anything in Perl:
189 .sp
190 \fB/8\fP PCRE_UTF8
191 \fB/?\fP PCRE_NO_UTF8_CHECK
192 \fB/A\fP PCRE_ANCHORED
193 \fB/C\fP PCRE_AUTO_CALLOUT
194 \fB/E\fP PCRE_DOLLAR_ENDONLY
195 \fB/f\fP PCRE_FIRSTLINE
196 \fB/J\fP PCRE_DUPNAMES
197 \fB/N\fP PCRE_NO_AUTO_CAPTURE
198 \fB/U\fP PCRE_UNGREEDY
199 \fB/W\fP PCRE_UCP
200 \fB/X\fP PCRE_EXTRA
201 \fB/Y\fP PCRE_NO_START_OPTIMIZE
202 \fB/<JS>\fP PCRE_JAVASCRIPT_COMPAT
203 \fB/<cr>\fP PCRE_NEWLINE_CR
204 \fB/<lf>\fP PCRE_NEWLINE_LF
205 \fB/<crlf>\fP PCRE_NEWLINE_CRLF
206 \fB/<anycrlf>\fP PCRE_NEWLINE_ANYCRLF
207 \fB/<any>\fP PCRE_NEWLINE_ANY
208 \fB/<bsr_anycrlf>\fP PCRE_BSR_ANYCRLF
209 \fB/<bsr_unicode>\fP PCRE_BSR_UNICODE
210 .sp
211 The modifiers that are enclosed in angle brackets are literal strings as shown,
212 including the angle brackets, but the letters within can be in either case.
213 This example sets multiline matching with CRLF as the line ending sequence:
214 .sp
215 /^abc/m<CRLF>
216 .sp
217 As well as turning on the PCRE_UTF8 option, the \fB/8\fP modifier also causes
218 any non-printing characters in output strings to be printed using the
219 \ex{hh...} notation if they are valid UTF-8 sequences. Full details of the PCRE
220 options are given in the
221 .\" HREF
222 \fBpcreapi\fP
223 .\"
224 documentation.
225 .
226 .
227 .SS "Finding all matches in a string"
228 .rs
229 .sp
230 Searching for all possible matches within each subject string can be requested
231 by the \fB/g\fP or \fB/G\fP modifier. After finding a match, PCRE is called
232 again to search the remainder of the subject string. The difference between
233 \fB/g\fP and \fB/G\fP is that the former uses the \fIstartoffset\fP argument to
234 \fBpcre_exec()\fP to start searching at a new point within the entire string
235 (which is in effect what Perl does), whereas the latter passes over a shortened
236 substring. This makes a difference to the matching process if the pattern
237 begins with a lookbehind assertion (including \eb or \eB).
238 .P
239 If any call to \fBpcre_exec()\fP in a \fB/g\fP or \fB/G\fP sequence matches an
240 empty string, the next call is done with the PCRE_NOTEMPTY_ATSTART and
241 PCRE_ANCHORED flags set in order to search for another, non-empty, match at the
242 same point. If this second match fails, the start offset is advanced, and the
243 normal match is retried. This imitates the way Perl handles such cases when
244 using the \fB/g\fP modifier or the \fBsplit()\fP function. Normally, the start
245 offset is advanced by one character, but if the newline convention recognizes
246 CRLF as a newline, and the current character is CR followed by LF, an advance
247 of two is used.
248 .
249 .
250 .SS "Other modifiers"
251 .rs
252 .sp
253 There are yet more modifiers for controlling the way \fBpcretest\fP
254 operates.
255 .P
256 The \fB/+\fP modifier requests that as well as outputting the substring that
257 matched the entire pattern, pcretest should in addition output the remainder of
258 the subject string. This is useful for tests where the subject contains
259 multiple copies of the same substring.
260 .P
261 The \fB/B\fP modifier is a debugging feature. It requests that \fBpcretest\fP
262 output a representation of the compiled byte code after compilation. Normally
263 this information contains length and offset values; however, if \fB/Z\fP is
264 also present, this data is replaced by spaces. This is a special feature for
265 use in the automatic test scripts; it ensures that the same output is generated
266 for different internal link sizes.
267 .P
268 The \fB/D\fP modifier is a PCRE debugging feature, and is equivalent to
269 \fB/BI\fP, that is, both the \fB/B\fP and the \fB/I\fP modifiers.
270 .P
271 The \fB/F\fP modifier causes \fBpcretest\fP to flip the byte order of the
272 fields in the compiled pattern that contain 2-byte and 4-byte numbers. This
273 facility is for testing the feature in PCRE that allows it to execute patterns
274 that were compiled on a host with a different endianness. This feature is not
275 available when the POSIX interface to PCRE is being used, that is, when the
276 \fB/P\fP pattern modifier is specified. See also the section about saving and
277 reloading compiled patterns below.
278 .P
279 The \fB/I\fP modifier requests that \fBpcretest\fP output information about the
280 compiled pattern (whether it is anchored, has a fixed first character, and
281 so on). It does this by calling \fBpcre_fullinfo()\fP after compiling a
282 pattern. If the pattern is studied, the results of that are also output.
283 .P
284 The \fB/K\fP modifier requests \fBpcretest\fP to show names from backtracking
285 control verbs that are returned from calls to \fBpcre_exec()\fP. It causes
286 \fBpcretest\fP to create a \fBpcre_extra\fP block if one has not already been
287 created by a call to \fBpcre_study()\fP, and to set the PCRE_EXTRA_MARK flag
288 and the \fBmark\fP field within it, every time that \fBpcre_exec()\fP is
289 called. If the variable that the \fBmark\fP field points to is non-NULL for a
290 match, non-match, or partial match, \fBpcretest\fP prints the string to which
291 it points. For a match, this is shown on a line by itself, tagged with "MK:".
292 For a non-match it is added to the message.
293 .P
294 The \fB/L\fP modifier must be followed directly by the name of a locale, for
295 example,
296 .sp
297 /pattern/Lfr_FR
298 .sp
299 For this reason, it must be the last modifier. The given locale is set,
300 \fBpcre_maketables()\fP is called to build a set of character tables for the
301 locale, and this is then passed to \fBpcre_compile()\fP when compiling the
302 regular expression. Without an \fB/L\fP (or \fB/T\fP) modifier, NULL is passed
303 as the tables pointer; that is, \fB/L\fP applies only to the expression on
304 which it appears.
305 .P
306 The \fB/M\fP modifier causes the size of memory block used to hold the compiled
307 pattern to be output.
308 .P
309 If the \fB/S\fP modifier appears once, it causes \fBpcre_study()\fP to be
310 called after the expression has been compiled, and the results used when the
311 expression is matched. If \fB/S\fP appears twice, it suppresses studying, even
312 if it was requested externally by the \fB-s\fP command line option. This makes
313 it possible to specify that certain patterns are always studied, and others are
314 never studied, independently of \fB-s\fP. This feature is used in the test
315 files in a few cases where the output is different when the pattern is studied.
316 .P
317 The \fB/T\fP modifier must be followed by a single digit. It causes a specific
318 set of built-in character tables to be passed to \fBpcre_compile()\fP. It is
319 used in the standard PCRE tests to check behaviour with different character
320 tables. The digit specifies the tables as follows:
321 .sp
322 0 the default ASCII tables, as distributed in
323 pcre_chartables.c.dist
324 1 a set of tables defining ISO 8859 characters
325 .sp
326 In table 1, some characters whose codes are greater than 128 are identified as
327 letters, digits, spaces, etc.
328 .
329 .
330 .SS "Using the POSIX wrapper API"
331 .rs
332 .sp
333 The \fB/P\fP modifier causes \fBpcretest\fP to call PCRE via the POSIX wrapper
334 API rather than its native API. When \fB/P\fP is set, the following modifiers
335 set options for the \fBregcomp()\fP function:
336 .sp
337 /i REG_ICASE
338 /m REG_NEWLINE
339 /N REG_NOSUB
340 /s REG_DOTALL )
341 /U REG_UNGREEDY ) These options are not part of
342 /W REG_UCP ) the POSIX standard
343 /8 REG_UTF8 )
344 .sp
345 The \fB/+\fP modifier works as described above. All other modifiers are
346 ignored.
347 .
348 .
349 .SH "DATA LINES"
350 .rs
351 .sp
352 Before each data line is passed to \fBpcre_exec()\fP, leading and trailing
353 white space is removed, and it is then scanned for \e escapes. Some of these
354 are pretty esoteric features, intended for checking out some of the more
355 complicated features of PCRE. If you are just testing "ordinary" regular
356 expressions, you probably don't need any of these. The following escapes are
357 recognized:
358 .sp
359 \ea alarm (BEL, \ex07)
360 \eb backspace (\ex08)
361 \ee escape (\ex27)
362 \ef form feed (\ex0c)
363 \en newline (\ex0a)
364 .\" JOIN
365 \eqdd set the PCRE_MATCH_LIMIT limit to dd
366 (any number of digits)
367 \er carriage return (\ex0d)
368 \et tab (\ex09)
369 \ev vertical tab (\ex0b)
370 \ennn octal character (up to 3 octal digits)
371 always a byte unless > 255 in UTF-8 mode
372 \exhh hexadecimal byte (up to 2 hex digits)
373 .\" JOIN
374 \ex{hh...} hexadecimal character, any number of digits
375 in UTF-8 mode
376 .\" JOIN
377 \eA pass the PCRE_ANCHORED option to \fBpcre_exec()\fP
378 or \fBpcre_dfa_exec()\fP
379 .\" JOIN
380 \eB pass the PCRE_NOTBOL option to \fBpcre_exec()\fP
381 or \fBpcre_dfa_exec()\fP
382 .\" JOIN
383 \eCdd call pcre_copy_substring() for substring dd
384 after a successful match (number less than 32)
385 .\" JOIN
386 \eCname call pcre_copy_named_substring() for substring
387 "name" after a successful match (name termin-
388 ated by next non alphanumeric character)
389 .\" JOIN
390 \eC+ show the current captured substrings at callout
391 time
392 \eC- do not supply a callout function
393 .\" JOIN
394 \eC!n return 1 instead of 0 when callout number n is
395 reached
396 .\" JOIN
397 \eC!n!m return 1 instead of 0 when callout number n is
398 reached for the nth time
399 .\" JOIN
400 \eC*n pass the number n (may be negative) as callout
401 data; this is used as the callout return value
402 \eD use the \fBpcre_dfa_exec()\fP match function
403 \eF only shortest match for \fBpcre_dfa_exec()\fP
404 .\" JOIN
405 \eGdd call pcre_get_substring() for substring dd
406 after a successful match (number less than 32)
407 .\" JOIN
408 \eGname call pcre_get_named_substring() for substring
409 "name" after a successful match (name termin-
410 ated by next non-alphanumeric character)
411 .\" JOIN
412 \eL call pcre_get_substringlist() after a
413 successful match
414 .\" JOIN
415 \eM discover the minimum MATCH_LIMIT and
416 MATCH_LIMIT_RECURSION settings
417 .\" JOIN
418 \eN pass the PCRE_NOTEMPTY option to \fBpcre_exec()\fP
419 or \fBpcre_dfa_exec()\fP; if used twice, pass the
420 PCRE_NOTEMPTY_ATSTART option
421 .\" JOIN
422 \eOdd set the size of the output vector passed to
423 \fBpcre_exec()\fP to dd (any number of digits)
424 .\" JOIN
425 \eP pass the PCRE_PARTIAL_SOFT option to \fBpcre_exec()\fP
426 or \fBpcre_dfa_exec()\fP; if used twice, pass the
427 PCRE_PARTIAL_HARD option
428 .\" JOIN
429 \eQdd set the PCRE_MATCH_LIMIT_RECURSION limit to dd
430 (any number of digits)
431 \eR pass the PCRE_DFA_RESTART option to \fBpcre_dfa_exec()\fP
432 \eS output details of memory get/free calls during matching
433 .\" JOIN
434 \eY pass the PCRE_NO_START_OPTIMIZE option to \fBpcre_exec()\fP
435 or \fBpcre_dfa_exec()\fP
436 .\" JOIN
437 \eZ pass the PCRE_NOTEOL option to \fBpcre_exec()\fP
438 or \fBpcre_dfa_exec()\fP
439 .\" JOIN
440 \e? pass the PCRE_NO_UTF8_CHECK option to
441 \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
442 .\" JOIN
443 \e>dd start the match at offset dd (optional "-"; then
444 any number of digits); this sets the \fIstartoffset\fP
445 argument for \fBpcre_exec()\fP or \fBpcre_dfa_exec()\fP
446 .\" JOIN
447 \e<cr> pass the PCRE_NEWLINE_CR option to \fBpcre_exec()\fP
448 or \fBpcre_dfa_exec()\fP
449 .\" JOIN
450 \e<lf> pass the PCRE_NEWLINE_LF option to \fBpcre_exec()\fP
451 or \fBpcre_dfa_exec()\fP
452 .\" JOIN
453 \e<crlf> pass the PCRE_NEWLINE_CRLF option to \fBpcre_exec()\fP
454 or \fBpcre_dfa_exec()\fP
455 .\" JOIN
456 \e<anycrlf> pass the PCRE_NEWLINE_ANYCRLF option to \fBpcre_exec()\fP
457 or \fBpcre_dfa_exec()\fP
458 .\" JOIN
459 \e<any> pass the PCRE_NEWLINE_ANY option to \fBpcre_exec()\fP
460 or \fBpcre_dfa_exec()\fP
461 .sp
462 Note that \exhh always specifies one byte, even in UTF-8 mode; this makes it
463 possible to construct invalid UTF-8 sequences for testing purposes. On the
464 other hand, \ex{hh} is interpreted as a UTF-8 character in UTF-8 mode,
465 generating more than one byte if the value is greater than 127. When not in
466 UTF-8 mode, it generates one byte for values less than 256, and causes an error
467 for greater values.
468 .P
469 The escapes that specify line ending sequences are literal strings, exactly as
470 shown. No more than one newline setting should be present in any data line.
471 .P
472 A backslash followed by anything else just escapes the anything else. If
473 the very last character is a backslash, it is ignored. This gives a way of
474 passing an empty line as data, since a real empty line terminates the data
475 input.
476 .P
477 If \eM is present, \fBpcretest\fP calls \fBpcre_exec()\fP several times, with
478 different values in the \fImatch_limit\fP and \fImatch_limit_recursion\fP
479 fields of the \fBpcre_extra\fP data structure, until it finds the minimum
480 numbers for each parameter that allow \fBpcre_exec()\fP to complete. The
481 \fImatch_limit\fP number is a measure of the amount of backtracking that takes
482 place, and checking it out can be instructive. For most simple matches, the
483 number is quite small, but for patterns with very large numbers of matching
484 possibilities, it can become large very quickly with increasing length of
485 subject string. The \fImatch_limit_recursion\fP number is a measure of how much
486 stack (or, if PCRE is compiled with NO_RECURSE, how much heap) memory is needed
487 to complete the match attempt.
488 .P
489 When \eO is used, the value specified may be higher or lower than the size set
490 by the \fB-O\fP command line option (or defaulted to 45); \eO applies only to
491 the call of \fBpcre_exec()\fP for the line in which it appears.
492 .P
493 If the \fB/P\fP modifier was present on the pattern, causing the POSIX wrapper
494 API to be used, the only option-setting sequences that have any effect are \eB,
495 \eN, and \eZ, causing REG_NOTBOL, REG_NOTEMPTY, and REG_NOTEOL, respectively,
496 to be passed to \fBregexec()\fP.
497 .P
498 The use of \ex{hh...} to represent UTF-8 characters is not dependent on the use
499 of the \fB/8\fP modifier on the pattern. It is recognized always. There may be
500 any number of hexadecimal digits inside the braces. The result is from one to
501 six bytes, encoded according to the original UTF-8 rules of RFC 2279. This
502 allows for values in the range 0 to 0x7FFFFFFF. Note that not all of those are
503 valid Unicode code points, or indeed valid UTF-8 characters according to the
504 later rules in RFC 3629.
505 .
506 .
507 .SH "THE ALTERNATIVE MATCHING FUNCTION"
508 .rs
509 .sp
510 By default, \fBpcretest\fP uses the standard PCRE matching function,
511 \fBpcre_exec()\fP to match each data line. From release 6.0, PCRE supports an
512 alternative matching function, \fBpcre_dfa_test()\fP, which operates in a
513 different way, and has some restrictions. The differences between the two
514 functions are described in the
515 .\" HREF
516 \fBpcrematching\fP
517 .\"
518 documentation.
519 .P
520 If a data line contains the \eD escape sequence, or if the command line
521 contains the \fB-dfa\fP option, the alternative matching function is called.
522 This function finds all possible matches at a given point. If, however, the \eF
523 escape sequence is present in the data line, it stops after the first match is
524 found. This is always the shortest possible match.
525 .
526 .
527 .SH "DEFAULT OUTPUT FROM PCRETEST"
528 .rs
529 .sp
530 This section describes the output when the normal matching function,
531 \fBpcre_exec()\fP, is being used.
532 .P
533 When a match succeeds, \fBpcretest\fP outputs the list of captured substrings
534 that \fBpcre_exec()\fP returns, starting with number 0 for the string that
535 matched the whole pattern. Otherwise, it outputs "No match" when the return is
536 PCRE_ERROR_NOMATCH, and "Partial match:" followed by the partially matching
537 substring when \fBpcre_exec()\fP returns PCRE_ERROR_PARTIAL. (Note that this is
538 the entire substring that was inspected during the partial match; it may
539 include characters before the actual match start if a lookbehind assertion,
540 \eK, \eb, or \eB was involved.) For any other return, \fBpcretest\fP outputs
541 the PCRE negative error number and a short descriptive phrase. If the error is
542 a failed UTF-8 string check, the byte offset of the start of the failing
543 character and the reason code are also output, provided that the size of the
544 output vector is at least two. Here is an example of an interactive
545 \fBpcretest\fP run.
546 .sp
547 $ pcretest
548 PCRE version 8.13 2011-04-30
549 .sp
550 re> /^abc(\ed+)/
551 data> abc123
552 0: abc123
553 1: 123
554 data> xyz
555 No match
556 .sp
557 Unset capturing substrings that are not followed by one that is set are not
558 returned by \fBpcre_exec()\fP, and are not shown by \fBpcretest\fP. In the
559 following example, there are two capturing substrings, but when the first data
560 line is matched, the second, unset substring is not shown. An "internal" unset
561 substring is shown as "<unset>", as for the second data line.
562 .sp
563 re> /(a)|(b)/
564 data> a
565 0: a
566 1: a
567 data> b
568 0: b
569 1: <unset>
570 2: b
571 .sp
572 If the strings contain any non-printing characters, they are output as \e0x
573 escapes, or as \ex{...} escapes if the \fB/8\fP modifier was present on the
574 pattern. See below for the definition of non-printing characters. If the
575 pattern has the \fB/+\fP modifier, the output for substring 0 is followed by
576 the the rest of the subject string, identified by "0+" like this:
577 .sp
578 re> /cat/+
579 data> cataract
580 0: cat
581 0+ aract
582 .sp
583 If the pattern has the \fB/g\fP or \fB/G\fP modifier, the results of successive
584 matching attempts are output in sequence, like this:
585 .sp
586 re> /\eBi(\ew\ew)/g
587 data> Mississippi
588 0: iss
589 1: ss
590 0: iss
591 1: ss
592 0: ipp
593 1: pp
594 .sp
595 "No match" is output only if the first match attempt fails. Here is an example
596 of a failure message (the offset 4 that is specified by \e>4 is past the end of
597 the subject string):
598 .sp
599 re> /xyz/
600 data> xyz\>4
601 Error -24 (bad offset value)
602 .P
603 If any of the sequences \fB\eC\fP, \fB\eG\fP, or \fB\eL\fP are present in a
604 data line that is successfully matched, the substrings extracted by the
605 convenience functions are output with C, G, or L after the string number
606 instead of a colon. This is in addition to the normal full list. The string
607 length (that is, the return from the extraction function) is given in
608 parentheses after each string for \fB\eC\fP and \fB\eG\fP.
609 .P
610 Note that whereas patterns can be continued over several lines (a plain ">"
611 prompt is used for continuations), data lines may not. However newlines can be
612 included in data by means of the \en escape (or \er, \er\en, etc., depending on
613 the newline sequence setting).
614 .
615 .
616 .
617 .SH "OUTPUT FROM THE ALTERNATIVE MATCHING FUNCTION"
618 .rs
619 .sp
620 When the alternative matching function, \fBpcre_dfa_exec()\fP, is used (by
621 means of the \eD escape sequence or the \fB-dfa\fP command line option), the
622 output consists of a list of all the matches that start at the first point in
623 the subject where there is at least one match. For example:
624 .sp
625 re> /(tang|tangerine|tan)/
626 data> yellow tangerine\eD
627 0: tangerine
628 1: tang
629 2: tan
630 .sp
631 (Using the normal matching function on this data finds only "tang".) The
632 longest matching string is always given first (and numbered zero). After a
633 PCRE_ERROR_PARTIAL return, the output is "Partial match:", followed by the
634 partially matching substring. (Note that this is the entire substring that was
635 inspected during the partial match; it may include characters before the actual
636 match start if a lookbehind assertion, \eK, \eb, or \eB was involved.)
637 .P
638 If \fB/g\fP is present on the pattern, the search for further matches resumes
639 at the end of the longest match. For example:
640 .sp
641 re> /(tang|tangerine|tan)/g
642 data> yellow tangerine and tangy sultana\eD
643 0: tangerine
644 1: tang
645 2: tan
646 0: tang
647 1: tan
648 0: tan
649 .sp
650 Since the matching function does not support substring capture, the escape
651 sequences that are concerned with captured substrings are not relevant.
652 .
653 .
654 .SH "RESTARTING AFTER A PARTIAL MATCH"
655 .rs
656 .sp
657 When the alternative matching function has given the PCRE_ERROR_PARTIAL return,
658 indicating that the subject partially matched the pattern, you can restart the
659 match with additional subject data by means of the \eR escape sequence. For
660 example:
661 .sp
662 re> /^\ed?\ed(jan|feb|mar|apr|may|jun|jul|aug|sep|oct|nov|dec)\ed\ed$/
663 data> 23ja\eP\eD
664 Partial match: 23ja
665 data> n05\eR\eD
666 0: n05
667 .sp
668 For further information about partial matching, see the
669 .\" HREF
670 \fBpcrepartial\fP
671 .\"
672 documentation.
673 .
674 .
675 .SH CALLOUTS
676 .rs
677 .sp
678 If the pattern contains any callout requests, \fBpcretest\fP's callout function
679 is called during matching. This works with both matching functions. By default,
680 the called function displays the callout number, the start and current
681 positions in the text at the callout time, and the next pattern item to be
682 tested. For example, the output
683 .sp
684 --->pqrabcdef
685 0 ^ ^ \ed
686 .sp
687 indicates that callout number 0 occurred for a match attempt starting at the
688 fourth character of the subject string, when the pointer was at the seventh
689 character of the data, and when the next pattern item was \ed. Just one
690 circumflex is output if the start and current positions are the same.
691 .P
692 Callouts numbered 255 are assumed to be automatic callouts, inserted as a
693 result of the \fB/C\fP pattern modifier. In this case, instead of showing the
694 callout number, the offset in the pattern, preceded by a plus, is output. For
695 example:
696 .sp
697 re> /\ed?[A-E]\e*/C
698 data> E*
699 --->E*
700 +0 ^ \ed?
701 +3 ^ [A-E]
702 +8 ^^ \e*
703 +10 ^ ^
704 0: E*
705 .sp
706 The callout function in \fBpcretest\fP returns zero (carry on matching) by
707 default, but you can use a \eC item in a data line (as described above) to
708 change this.
709 .P
710 Inserting callouts can be helpful when using \fBpcretest\fP to check
711 complicated regular expressions. For further information about callouts, see
712 the
713 .\" HREF
714 \fBpcrecallout\fP
715 .\"
716 documentation.
717 .
718 .
719 .
720 .SH "NON-PRINTING CHARACTERS"
721 .rs
722 .sp
723 When \fBpcretest\fP is outputting text in the compiled version of a pattern,
724 bytes other than 32-126 are always treated as non-printing characters are are
725 therefore shown as hex escapes.
726 .P
727 When \fBpcretest\fP is outputting text that is a matched part of a subject
728 string, it behaves in the same way, unless a different locale has been set for
729 the pattern (using the \fB/L\fP modifier). In this case, the \fBisprint()\fP
730 function to distinguish printing and non-printing characters.
731 .
732 .
733 .
734 .SH "SAVING AND RELOADING COMPILED PATTERNS"
735 .rs
736 .sp
737 The facilities described in this section are not available when the POSIX
738 interface to PCRE is being used, that is, when the \fB/P\fP pattern modifier is
739 specified.
740 .P
741 When the POSIX interface is not in use, you can cause \fBpcretest\fP to write a
742 compiled pattern to a file, by following the modifiers with > and a file name.
743 For example:
744 .sp
745 /pattern/im >/some/file
746 .sp
747 See the
748 .\" HREF
749 \fBpcreprecompile\fP
750 .\"
751 documentation for a discussion about saving and re-using compiled patterns.
752 .P
753 The data that is written is binary. The first eight bytes are the length of the
754 compiled pattern data followed by the length of the optional study data, each
755 written as four bytes in big-endian order (most significant byte first). If
756 there is no study data (either the pattern was not studied, or studying did not
757 return any data), the second length is zero. The lengths are followed by an
758 exact copy of the compiled pattern. If there is additional study data, this
759 follows immediately after the compiled pattern. After writing the file,
760 \fBpcretest\fP expects to read a new pattern.
761 .P
762 A saved pattern can be reloaded into \fBpcretest\fP by specifying < and a file
763 name instead of a pattern. The name of the file must not contain a < character,
764 as otherwise \fBpcretest\fP will interpret the line as a pattern delimited by <
765 characters.
766 For example:
767 .sp
768 re> </some/file
769 Compiled pattern loaded from /some/file
770 No study data
771 .sp
772 When the pattern has been loaded, \fBpcretest\fP proceeds to read data lines in
773 the usual way.
774 .P
775 You can copy a file written by \fBpcretest\fP to a different host and reload it
776 there, even if the new host has opposite endianness to the one on which the
777 pattern was compiled. For example, you can compile on an i86 machine and run on
778 a SPARC machine.
779 .P
780 File names for saving and reloading can be absolute or relative, but note that
781 the shell facility of expanding a file name that starts with a tilde (~) is not
782 available.
783 .P
784 The ability to save and reload files in \fBpcretest\fP is intended for testing
785 and experimentation. It is not intended for production use because only a
786 single pattern can be written to a file. Furthermore, there is no facility for
787 supplying custom character tables for use with a reloaded pattern. If the
788 original pattern was compiled with custom tables, an attempt to match a subject
789 string using a reloaded pattern is likely to cause \fBpcretest\fP to crash.
790 Finally, if you attempt to load a file that is not in the correct format, the
791 result is undefined.
792 .
793 .
794 .SH "SEE ALSO"
795 .rs
796 .sp
797 \fBpcre\fP(3), \fBpcreapi\fP(3), \fBpcrecallout\fP(3), \fBpcrematching\fP(3),
798 \fBpcrepartial\fP(d), \fBpcrepattern\fP(3), \fBpcreprecompile\fP(3).
799 .
800 .
801 .SH AUTHOR
802 .rs
803 .sp
804 .nf
805 Philip Hazel
806 University Computing Service
807 Cambridge CB2 3QH, England.
808 .fi
809 .
810 .
811 .SH REVISION
812 .rs
813 .sp
814 .nf
815 Last updated: 02 July 2011
816 Copyright (c) 1997-2011 University of Cambridge.
817 .fi

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